The Final Sin: Nanatsu No Taizai
by AzralarTheArchangel
Summary: Acnologia, after his defeat at the hands of Natsu Dragneel, get's sent to another world. After a series of events, and the death of a member of the Seven Deadly Sins... He takes the place of the fallen sin, and starts his journey to atone for his past sins. Enter, The Seven Deadly Sins, The Sin of Hatred, The Demons Sin Acnologia! By SolGodofTheStars-Wattpad Aka AzralarTheArchangel
1. Chapter 1

_This is a Fairy Tail X Nanatsu No Taizai Fanfiction, I do not own either series and all credit goes to the authors of each series Hiro Mashima (Fairy Tail) and_ _Nakaba Suzuki (Nanatsu No Taizai) as well as the publishing companies who also own the rights Kodansha/Weekly Shonen Magazine._

 _"This is what is looks like when a character talks out loud."  
Thoughts can appear in two forms... 'like this with the single quote marks' or as a statement like this... (Dialogue/Event) What is the squirrel doing in that bucket? without the single quotes mark._

Acnologia desperately reached out, trying to push his magic out, but no matter how hard he tried, his magic would not answer his call. His body was burning, and he couldn't do anything about it. "There is no blood..." Acnologia longed for the familiar scent. "My destruction... there are no tears..." He longed for the destruction that would satisfy him, but it never could. "Everything my ha- hands wanted..." Acnologia felt his body fading away, the flame brat was hunched over, out of breath and bleeding all over, but smiling that familiar smile. _'That smile... I wanted to destroy it...'_

"You would never have been able to destroy everything. You'd never get everything." What is the boy talking about? Acnologia's mind was beginning to follow suit with his body, fading quickly. "Because you don't have the most precious thing of all, something to protect... I don't need anything else, Because I have my family." It hit him then, finally, why the boy seemed so familiar, a warm feeling came up from somewhere deep inside and a single tear fell from The Dragon King's eye.

"I see... You are indeed worthy, of being The Dragon King..." he was almost gone now, he couldn't hardly believe it, four hundred years and it was all finally over. The last thing he heard before the silence took him was the boys voice. "I don't need to be the King." why did he sound so cheerful? It didn't matter now, the darkness was all that there was left, Acnologia let it embrace him and he sank deeper and deeper. "So this is what it feels like to die? I welcome the peace if nothing else..." Acnologia sighed internally one last time, his final breath.

 _Chapter 1.2 The King awakens in a strange world._

Acnologia let his gaze wander across the blue expanse of the sky, this couldn't possibly be the afterlife. Acnologia was no fool, he knew that when he died if he ever did that he had a one way ticket to Purgatory, yet this place... was calm and peaceful. The breeze flew through the trees and the leafy branches swayed with the movement of the wind, the birds were chirping and the woodland creatures were scurrying about the ground. He rose to a sitting position, and observed his surroundings. Everywhere he looked there were trees, and the large open space he was in, was filled with flowers and a small pond, he noticed the ducklings playing in the water, and the deer drinking from it as well.

'This... I am not dead. My heart still beats in my chest, and my magic... it seems that I have exhausted my supply, but it is still there.' He rose to his feet, pain shot through his body and he fell back to his knees, his cloak was in in tatters and no longer useful. His left pant leg had been completely incinerated by the flame dragon, and across his body, he was bleeding in multiple locations. "Well if that isn't a sure sign that I am alive... I don't know what is." He cautiously rose to his feet again, and limped over to a tree, and with what little strength he had he broke off a branch to use as a walking stick.

"First things first, I need to find my way out of this forest." He tested his senses. Good, they were still heightened, he tested the air. "I guess I will go that way, the sooner I get medical attention the sooner I can find out where the hell I am." Acnologia walked off in the direction he had chosen, leaving the grove behind and heading eagerly for civilization, and for the first time in a long time. He actually felt calm.

 _A short while later._

Acnologia, after walking for what couldn't have been less than an hour stumbled up to a small building, it smelled of alcohol and food, and something a bit more ominous. He couldn't worry about that right now, he could barely maintain his consciousness. It had taken more out of him than he thought it would to reach this place. His injuries were far worse than he had originally thought, a few townsfolk noticed him and immediately ran over to help. "Sir, are you okay!?" he struggled to form words but at this point he couldn't go on any longer, the world turned upside down and then everything went black.

Acnologia awoke to a girl standing over him, a glowing energy emanating from her hands. The blue light washed over his aching body, and his pain seemed to be slowly fading away. "Healing magic... that's a rare ability if I ever saw one..." He growled through his teeth as he tried to sit up, 'It's still not completely healed yet.' the girl smiled slightly but didn't say a word, as she tried to maintain her focus. "Where am I?" He asked her.

"The Boar Hat's Bar!" A cheerful voice came from his right, he looked over. A small boy with blonde hair as well as an older man, wearing tight red leather clothing and a very feminine looking man with pink hair stood behind him. They were an odd looking group. The blonde kid waved at him with a huge grin plastered all over his face, "Yo!" Acnologia stared at him for a moment, and then just nodded awkwardly. "I see... how far away am I from Fiore?" The boy looked confused, and the pink haired man answered for him. "Fiore is not a country that exists within Britannia, do you come from another land that I have not heard of?" Acnologia raised an eyebrow. "Britannia?" The man nodded. "You are in the kingdom of Liones."

'There is just no way... I am not even on Earthland any more?' Acnologia had been struggling to face this truth for the past hour now. He had been healed enough by the girl, whose name he had found out was Elizabeth. He was in the main room of the bar now, sitting at the counter drinking a flagon cup of water. "So, we never caught your name. Care to share?" Acnologia stared at the kid, or... at least he had mistaken him for a kid. In truth, Meliodas for that was his name, was an adult contrary to his appearance. Acnologia still not believing he wasn't on Earthland. He responded truthfully, realizing this was the one way to find out. "My name is Acnologia." he waited for their response, hoping they would react with fear, giving away that he was still in the world of his origin. "Nice to meet you!" Meliodas responded cheerfully.

"You already met Elizabeth and Gowther! That one with the spiky hair that looks all mean is Ban!" Acnologia glanced at each one of them, giving them a slight nod. He could feel their power, and it was nothing to scoff at, besides the fact that they were the ones who were giving him food and shelter as well as healing. "Meliodas." Meliodas cocked an eyebrow at Acnologia's direct and rather rude way of getting his attention. Acnologia gestured to his surroundings. "What are three beings of your caliber, doing operating a bar such as this? I can feel the magic power emanating from you three, and it is massive." Meliodas looked thoughtful for a moment and then he responded. "We run the bar for fun, as well as a home to come back to after our missions."

"Missions?" Meliodas shot him a thumbs up, "Yep! We are The Seven Deadly Sins, an order of Holy Knights who protect this kingdom." Acnologia gave a small chuckle and pointed out to Meliodas, "But there are only four of you." The one in red leather spoke up for the first time, Ban. "The others are on a mission right now, should be back before too long."

"Is that why I feel three more energy signatures approaching?" Acnologia questioned. The hairs on his arms were standing up straight and his spine was tingling, something was wrong... there was a smell on the wind, one that was all to familiar to him. Blood. Death. "It doesn't seem like a benevolent energy, I would be on the ready if I were you." Meliodas and Ban both stared at the door, their eyes wide with fear. "Did you say... three?" Acnologia was puzzled, the three signatures were roughly equal with their own, so why did they seem so afraid? "Yes, three." he stated firmly. Meliodas and Ban shot for the door, slamming it open and disappearing outside. Acnologia shot to his feet, looking at Gowther absolutely confused, Elizabeth ran after Meliodas and Ban, her face drained of all color. "What the hell is happening?!" Gowther slowly walked over to the door, and stood in the opening. "This was unexpected, and most certainly is not good. Not good at all." The man responded in a monotonic voice, almost as if he had no emotional response at all. 'He isn't afraid, what the hell could be going on.' Acnologia walked over to the door himself and looked out, three more figures had appeared, a tall very muscular man with ginger hair and a mustache, a woman with raven colored hair and who was severely under dressed, and a young looking boy floating in the air with a spear to his side, his eyes filled with tears, and anger emanating off of him like a furnace that was getting to hot. There was a girl in the tall mans arms, her skin was ghostly white, and her eyes staring blankly at nothing. Blood leaked from a gaping wound in stomach freely. It was clear to Acnologia, that no amount of healing would save this girl. She was already gone.

"Captain! Diane... Diane is dead."

 _A/N: Welp, here is the first chapter of my Nanatsu No Taizai and Fairy Tail crossover fanfiction. I sincerely apologize Diane fans! This was important for the story to continue the way I wanted it to. I hope you enjoyed the first chapter, I accept any and all criticism as long as it is constructive, so feel free to let me know about any gripes you have with either my portrayal of the characters, or the direction I am taking the story in! I hope you will continue reading. Chapter 2 will be out soon._


	2. 2 Death of a Sin, Tragic Parting

Acnologia sat atop the Boar Hat's bar, watching as the Sins stood vigil over their fallen comrades grave. The small brown haired boys name was Harlequin, or King as he went by... was openly crying his heart out to the skies. He had noticed the grievous injuries the girl had received and was mildly curious as to how she had considering he had felt the power emanating from her friends. Truth be told however, he could not have cared less about the girl herself. Acnologia was simply biding his time and waiting for his magic to return, and once it had, he was going to search for a way to return to Earthland. 'I will have to play along for now... Anyone here could easily kill me in this weakened state. Attacking them would be a mistake.'

Acnologia watched for almost an hour before he jumped off of the roof of the bar, and headed back inside where he knew Gowther had already retreated to. When he entered he approached Gowther who was sitting in a corner of the bar reading a book. "Gowther, the one who died out there. Who killed her?" the pink haired boy continued to read his book as he answered. "Judging by her wounds, she was likely killed by Derieri of the Ten Commandments. Her body was pulverized by sheer brute strength. The likelihood of this is ninety-two percent." Acnologia kicked his chair back, half leaning against the wall and resting his shoe-less feet on the table.

"The Ten Commandments eh? And who are these Ten Commandments?" Acnologia asked while staring at the ceiling.

"That is correct, the Ten Commandments. The elite of the Demon Clan, The Demon King's Chosen Ten who were bestowed with a commandment. They strike fear even into the Goddess clan." Acnologia cocked an eyebrow and smiled.  
"The Elite of the Demon Clan eh? I heard of a group like that once. The Nine Demon Gates. They died pitifully, I would have reveled in it if I wasn't otherwise preoccupied." Gowther ignored him and continued reading his book.

"So Gowther, where are these 'Ten Commandments'? I would like to pay them a visit." Gowther finally tore his eyes away from the book.  
"That is a terrible idea. The Ten Commandments are brutal and would likely kill you on sight." Acnologia smirked, must be pretty powerful if they can kill one of these monsters... they were nearly as powerful as himself if not a bit stronger. This didn't disturb Acnologia as he thought it would if he ever encountered someone more powerful than him, it only served to excite him.

"Of course they are. Well, interesting talk Gowther." Acnologia stood up and left without waiting to see if Gowther even acknowledged him. He approached a window near the front door of the building and looked outside, the other members of the Seven Deadly Sins were still hovering over the girls grave. "Foolish." he muttered to himself. He walked out the door and began walking in the direction opposite of the Sins, into the forest. He needed to clear his head and reflect on the events of the past two weeks. Had it really only been two weeks? Two weeks since the Black Mage entered his hideout on Mt. Zonia, and the war between Alvarez and Ishgar started. It didn't matter now, he continued walking deeper and deeper into the forest. He kept walking until he reached the meadow where he had first arrived into this world.

For what seemed like an eternity he floated in the crystal clear water, lying on his back and staring into the sky. It was moments like these where he felt almost normal, almost like the man that he was four hundred years ago. He reminisced on his past, mainly on the day that he became The Dragon King. His close friend drank from the goblet, and his body quickly began to convulse and shake... an explosion of hell fire, and when the smoke cleared it was not his close friend who stood there, but a massive dragon. The events of that day had lead him to fiercely throw himself into battle, to protect what little he had left. He eventually lost himself, lost himself to his bloodlust, he fell into a trance and for seven days, he killed, and he killed, and he killed. He killed until The Dragons were gone, forever. He had won the Dragon King Festival, and claimed the title of Dragon King for himself, he had changed his name on that day. Akuno the street rat from the lower districts of Crocus, became Acnologia The King of Dragons. "If I had to do it all again... I would... no mercy." he smiled at the thought. Acnologia still thought of himself as the Supreme King of The Dragons.

"But there were no dragons to be ruled. You killed them all didn't you?" Acnologia, startled, erupted from the water and with blinding speed, he rushed the man who had so effortlessly snuck up on him. Now standing behind him, an orb of magical energy barely contained within the palm of his hand and nearly pressed into Gowther's back.  
"Gowther, why were you invading my thoughts?" Acnologia growled into his ear, even Gowther surely recognized the threat behind his words. Gowther ignored the veiled threat and spoke plainly "I was not able to see everything before you closed off your mind. Why did you kill the dragons?" Acnologia scowled and let his magic dissipate. "None of your damn business." Acnologia began to stalk off towards the Boar Hat once more. "There was once dragons on this continent. They have long since disappeared. I wonder if they are the same dragons you killed." Acnologia ignored Gowther and continued walking along with a scowl.

as Acnologia trampled through the forest, his mood soured by Gowther's intrusion, he paid no heed to his sense of direction. After an hour had passed he had realized that he had climbed up the mountain behind the Boar Hat, and was nearing the peak. He looked down and smiled happy to be near the familiar realm he called his own. He was the King of Dragons, and no matter what world, the skies... well they belonged to him. He shifted into his preferred form, that of The Terrible Acnologia, King of Dragons. He launched himself into the bitter cold air, and took it into his lungs, relishing the chance to stretch his wings and explore. He flew for almost a half day exploring the skies of Britannia and mapping out the land below him, it would take more than one flight but he would eventually memorize the countries lay out. Eventually this entire world.

After a half day had passed he began flying back towards The Boar Hat. His injuries, although healed a fair bit, had still left a little bruising and he needed to return to rest.  
out of the blue a shock wave knocked Acnologia's flight pattern off and he had to re-steady himself, not long after a second, third, fourth and fifth shock wave fired off followed by five gigantic rapid booms. Judging from the delay they had to be a few hundred miles off the shore.  
Acnologia chose not to investigate, he needed rest and nothing he thought, could pose any true threat save maybe the sins he had met and possibly these commandments he had heard of. But surely he flew high enough that neither would have even noticed him.

 _ **ROARRRRRR!**_

A colossal sound struck Acnologia's ears, and dread filled his heart and mind. "Dammit! The Hunters found their way into this world..." Acnologia increased his speed, this was extremely disturbing to the Dragon King. The Hunters were the only dragons he had not managed to kill yet, five enormously powerful dragons that rivaled even him, their only purpose was to hunt down and kill Acnologia, they had tried many times in the past and failed, but their arrival in this world was not a good sign. He continued to fly, comforted by the fact that the hunters would not seek him out immediately, they would lay low for a few weeks, months even before making a move. This however did change his plans, he would have to make allies in this world if he intended to survive, he was not as strong as he was on Earthland and he knew it. He had lost roughly thirty percent of his original power in addition to his time rift powers. The Sins would be his only hope to survive. "Making friends with mortals... how disgusting." he snarled. It had to be done in order for him to find his way home eventually.

As he drew closer to the Boar Hat over the next few hours, he noticed ten more energy signatures, rapidly approaching the Boar Hat, "Those must be the commandments... they are indeed impressive." he thought outloud. "This will be my chance to gain their favor then, let's hunt some hell freaks."  
 _ **BOOM!**_

 _ **Just as Acnologia landed upon the far side of the mountains, an explosion of energy erupted from the boar hat. "REVENGE COUNTER!"  
Acnologia smiled, the battle had started not three minutes ago and listening to the sound, it seemed the sins had lost. Acnologia aimed his jump, and erupted from the mountain side, destroying the entire top half of the mountain in his explosive wake.  
ROARRRR!  
He landed directly behind the ten demonic figures, the sins all laying nearly unconscious behind them.  
The Demons eyes grew wide, as a magic circle appeared directly above them, shining light erupted from it and when the flash cleared. The Demons were gone, The Dragon tensed his wings, and flung himself to the skies, circling once and then firing off a blast at the mountain, completely disintegrating it.**_

He flew into the night sky, a sound akin to laughing erupting from his mouth.  
He would return the next day to check on his new friends.

A/N: I wanted this to come out sooner, but I got a bit lazy. Hopefully next chapter will be out sometime in the next 7 days! Thanks for the support! :D


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